And split NSSInitializer and SEInitializer into two implementations,
they are not the same on Windows, so it simplifies things if they're
also split on other platforms.

Change-Id: Ifc0ea7e35e804232ee492b7eea9c25662c9b499e
Reviewed-on: https://gerrit.libreoffice.org/52801Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>